The invention relates to a rolling mill stand for the production of rolled strip or sheet metal, with working rolls which are supported on supporting rolls or on intermediate rolls which are in turn supported on supporting rolls. At least one of these rolls has a barrel contour which runs over the entire effective barrel length and can be described by a non-linear function. The barrel contour of this at least one roll has chamfers in at least one of the marginal regions of its longitudinal extent and forms a corrected barrel contour in these marginal regions.
In four-high rolling mill stands or six-high rolling mill stands, it is common practice to equip at least the two working rolls or the two intermediate rolls (in the six-high stand), but in some cases also the supporting rolls, with a special barrel contour and to provide axially acting adjustment devices for these working rolls or supporting rolls, so that the roll nip contour can be set as a function of the current rolled strip profile.
A rolling mill stand of this type is already known, for example, from AT 410765 B. The roll barrel contour of these rolls known among specialists by the designation SmartCrown® can be described mathematically by a modified sine function. A suitable choice of the contour parameters results in this case in a cosinuoidal clear roll nip, the amplitude of which can be influenced in a directed way by the axial displacement of the rolls. The rolls of rolling mill stands may, however, also have many other barrel contours, which are for example distinguished by a contour shape that is cylindrical, bulging, concavely-convexly curved or curved in some other way.
When working rolls or intermediate rolls with the barrel contour known from AT 410765 B and cylindrically shaped supporting rolls are used in four-high or six-high rolling mill stands, as is normally customary, it is unavoidable that load distributions which are inhomogeneous occur between the supporting rolls and the directly adjacent rolls during continuous rolling operation. Since the crowning region to be covered with the aid of the contoured rolls is always determined by the requirements of the rolling process, such as, for example, by different process parameters, dimensions and deformation properties of the rolling stock, the displacement stroke of the contoured rolls is the only influencing variable with which the markedness of the inhomogeneity of the load distribution can be influenced. Such measures are characterized by the requirement for the producer of the rolling stock to produce strips and sheets with ever narrower tolerance ranges.
In addition, excessive edge pressings occur in conjunction with the other adjacent rolls, especially in the marginal regions of the supporting rolls. In order to avoid inadmissibly high edge pressings between the working rolls and supporting rolls or between the working rolls and intermediate rolls or intermediate rolls and supporting rolls, barrel ends of the rolls are usually chamfered and therefore have a clearance in these marginal regions. Clearances of this type are already known from EP 0 258 482 A1 or EP 1 228 818 A2. These clearances, in the case of contoured roll barrels, are formed in marginal regions with a barrel radius increasing toward the margin, by a cylindrical barrel end, as is illustrated in EP 0 258 482 A1, or, in the case of rolls with a cylindrical roll barrel contour, may be formed by a conical marginal region, as illustrated and described, for example, in EP 1 228 818 A2. In any event, where these known clearances are concerned, there is only a shift of the critical pressing from the barrel ends (edges) to the transition region between the remaining barrel contour and the contour of the chamfer, since, in this configuration of the chamfer, once again, a kink or bend or a kind of step formed in the contour profile of the roll barrel occurs.
WO 02/09896 A1 and WO 2005/058517 A1 disclose, for example, a two-stage rectified area of the barrel contour on working rolls in a four-high stand or on intermediate rolls on a six-high stand. Starting from the central barrel contour, a first rectified area is provided in the direction of the barrel end by applying an arc function, precisely the same problems as previously stated with respect to the earlier prior art occurring in the transitional region of the central barrel contour to the contour of the rectified areas. The first rectified area is followed by a second rectified area, which extends up to the barrel end of the roll and realizes a cylindrical barrel contour.